(1) Field of the Invention
The present invention relates to a monitor system comprising a plurality of cameras. In particular, the present invention relates to a monitor system in which each of the plurality of cameras operates in cooperation with the other cameras so that the whole monitoring area can be monitored.
(2) Description of the Related Art
A high-performance monitor which is impossible with only one camera can be achieved by using a plurality of cameras.
Conventionally, as a monitor system using a plurality of cameras, for example, Japanese Laid-Open Patent application No. 11-103457 discloses a technique. FIG. 1 is a diagram showing a structure of an apparatus which automatically adjusts detection areas of a plurality of cameras. In FIG. 1, a moving object detection specific camera 10011 changes its image capturing range using an attitude control unit 10012, the moving object detection specific camera 10011 capturing an image of an object to be detected in a wide image capturing range. And, a monitor specific camera 10021 changes its image capturing range using the attitude control unit 10022, the monitor specific camera 10021 capturing an enlarged image of the object to be detected. The image capturing range of each camera is determined using (i) a position of the object to be image-captured which is extracted from a captured image captured by the moving object detection specific camera 10011 in an image processing apparatus 10040 and (ii) a detection range of each camera, based on information previously stored in camera view angle storage units 10031 and 10032.
FIGS. 2, 3 and 4 are illustrations showing procedures for determining the image capturing range of each camera in the above mentioned apparatus. And, these illustrations show respective images captured by the moving object detection specific camera 10011, the respective images being divided into several blocks.
The image capturing range of the moving object detection specific camera 10011 is determined as follows. In the case where an object to be image-captured exists in the blocks shown with oblique lines, the attitude of the moving object detection specific camera 10011 is changed to the direction as shown with the arrows in respective blocks of FIG. 3 corresponding to each block position as shown in FIG. 2. And, the image capturing range of the camera is changed. The image capturing range of the moving object detection specific camera 10011 corresponding to each block position is previously determined by a person, and preset in the camera view angle storage unit 10031.
On the other hand, the image capturing range of the monitor specific camera 10021 is determined as follows. In the case where the object to be image-captured exists in the block positions as shown in FIG. 4, the attitude of the monitor specific camera 10021 is changed so that the image capturing range becomes as the part shown with broken lines. And the image capturing range of the camera is changed. The image capturing range of the monitor specific camera 10021 corresponding to each block position is previously determined by a person, and preset in the camera view angle storage unit 10032.
As described above, according to the monitor system as disclosed in the Japanese Laid-Open Patent application No. 11-103457, the wide-range image capturing within the monitoring area and the detailed image capturing of the predetermined object are simultaneously performed.
Also, as another conventional technique used for a monitor system using a plurality of cameras, there is a monitor system in which a wide range is monitored using moving cameras that can change image capturing positions (for example, refer to Japanese Laid-Open Patent application No. 2001-142138). FIG. 5 is a diagram showing the structure of the moving camera 10 described in the Japanese Laid-Open Patent application No. 2001-142138. As shown in FIG. 5, the moving camera 10 includes a casing 12 and a camera unit 14 attached to the bottom of the casing 12. And, the moving camera 10 can move along the rail 20. Inside the casing 12, general control units which control various functions, such as a programming controller unit for controlling the movement and a motor control unit for controlling the transport mechanism, are placed. And, these general control units can control a speed of moving on the orbit of the rail 20, positions, zoom and the like according to the purpose of monitoring. According to the structure as described above, the moving camera 10 performs image-capturing while moving on the orbit of the rail 20 set in a predetermined monitoring area inside a shop, for example, a rental video shop and the like as shown in FIG. 6. Thereby, monitoring can be performed using a small number of cameras so that there are few blind spots in the monitoring area.
Also, as another conventional technique for acquiring images by using a plurality of cameras, Japanese Laid-Open Patent application No. 07-303207 discloses an image capturing apparatus. In the case of acquiring a plurality of image information from a plurality of image capturing systems by using (i) the plurality of image capturing systems for capturing an object and (ii) a convergence angle control unit for providing an arbitrary convergence angle to each of the plurality of image capturing systems, this image capturing apparatus controls each convergence angle in a plurality of image capturing systems so that the overlapping area of the image capturing ranges among the plurality of image capturing systems can be kept within a constant range by using (i) image capturing information provided from a detection unit which detects image capturing conditions of the plurality of image capturing systems and (ii) image magnification information provided from a storage unit which previously stores the image magnification information of the plurality of image capturing systems. Thus, in the case where the plurality of image information is acquired from the plurality of image capturing systems, the image capturing range can be effectively used without missing the overlapping area of the image capturing range between the image capturing systems.
Moreover, as another conventional technique used for a monitor system using a plurality of cameras, Japanese Laid-Open Patent No. 08-265741 discloses an area monitor apparatus using video. This apparatus includes: a fixed pilot camera for monitoring the area; and one or more mobile remote-operated cameras for monitoring at least a part of the area. The pilot camera generates a signal indicating the area. The pilot camera determines the position of the moving object in the monitoring area, and generates a signal indicating the position of the object. The remote-operated camera tracks the object based on the signal indicating the position of the object. The pilot camera has a fisheye lens, thus has a wider view than the remote-operated camera. The area during the monitoring is divided into Cartesian coordinates, polar coordinates and global coordinates, and using these coordinates, an instruction to cause a computer to track the object can be provided to the remote-operated camera. The signal indicating the area is compressed and transmitted via a communication channel for the remote monitoring. Thus, the monitoring of the whole area and the monitoring of the moving object can be performed.
However, according to the conventional techniques disclosed in the above mentioned Japanese Laid-Open Patent applications, there is a problem that the structures and the functions of the cameras included in each system are fixed, and not flexible. Due to this problem, in the case where the system structure is extended or changed by increasing the number of cameras included in the monitor system or by breakdown of some of the cameras, the whole system must be restructured. For example, in the case where one camera breaks down, the monitor system cannot function.
For example, in the camera disclosed in the Japanese Laid-Open Patent application No. 11-103457, predetermined functions are provided respectively to the moving object detection specific camera 10011 which captures an image in a wide range and the monitor specific camera 10021 which captures an enlarged image of an object to be detected. And, it is not possible for the moving object detection specific camera 10011 and the monitor specific camera 10021 to operate in cooperation and to capture an image in a wider range than the range in which one moving object detection specific camera 10011 can capture the image. Also, it is not possible for one camera to substitute for the function of the other camera such as that the moving object detection specific camera 10011 captures an enlarged image of the area which is a blind spot for the monitor specific camera 10021. Therefore, it is necessary to previously determine the setting of the monitor specific camera 10021 so that the camera does not have a blind spot in the monitoring area.
Moreover, in the cooperating operations of the two cameras disclosed in the above mentioned Japanese Laid-Open Patent application No. 11-103457, each set of procedures for changing the image capturing details of the monitor specific camera 10021 is associated with each detection result of the object detected by the moving object detection specific camera 10011. For example, in the case where the number of the moving object detection specific camera 10011 is increased, and accuracy of the moving object detection is improved, it is necessary to newly associate all the combination patterns of the respective detection results detected by the plurality of moving object detection specific cameras 10011 with the operations of the monitor specific camera 10021.
According to the conventional techniques disclosed in the above mentioned Japanese Laid-Open Patent applications, a different function is provided to each of the plurality of cameras. Thereby, there is a problem that a blind spot can be easily generated in monitoring, and monitoring ability is not sufficient.
For example, the plurality of moving cameras 10 included in the monitor system disclosed in the Japanese Laid-Open Patent application No. 2001-142138 can perform monitoring with less blind spots in the monitoring area by capturing the image of the monitoring area while moving inside the monitoring area along with the orbit of the rail 20 within a constant time. However, it is not possible for all of the moving cameras to simultaneously continue monitoring the whole monitoring area. Therefore, for example, in the case where an intruder constantly moves in the area which is the blind spot of the moving camera 10 in association with the movement of the moving camera 10, the monitor system cannot detect the intruder.